<template>
<div>
  <div class="header-abs" v-show="showAbs">
    <router-link to="/">
      <div class="iconfont header-abs-back">&#xe624;</div>
    </router-link>
  </div>
  <div class="header-fixed" v-show="!showAbs" :style="opacityStyle">
    <router-link to="/">
      <div class="iconfont header-fixed-back">&#xe624;</div>
    </router-link>
    景点详情
  </div>
</div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showAbs: true,
      opacityStyle: {opcity: 0}
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop
      if (top > 60) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = {opacity}
        this.showAbs = false
      } else {
        this.showAbs = true
      }
    }
  },
  activated () {
    window.addEventListener('scroll', this.handleScroll)
  },
  /**
   * 因为此处将scroll绑定在了window 上 因此当页面从detail切换到其他页面的时候还可以触发该事件
   * 所以需要在该组件退出的时候清除该监听方法
   */
  deactivated () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style scoped lang="stylus">
  @import "~styles/varibles.styl"
  .header-abs
    position absolute
    z-index 9
    left: .2rem
    top: .2rem
    width .8rem
    height .8rem
    text-align center
    border-radius .4rem
    background rgba(0,0,0,.8)
    .header-abs-back
      color #ffffff
      font-size .4rem
  .header-fixed
    position fixed
    z-index 99
    top: 0
    left: 0
    width 100%
    height $headerHeight
    line-height $headerHeight
    text-align center
    color #ffffff
    background $bgColor
    font-size .32rem
    .header-fixed-back
      position absolute
      top 0
      left 0
      width .64rem
      text-align center
      font-size .4rem
      color #fff
</style>
